The present invention relates to a seat height adjuster drive for a vehicle seat, in particular for an automobile seat.
DE 44 00 910 A1 discloses a known seat height adjuster drive, whose stepping mechanism enables a pumping motion that is symmetrical in both directions of adjustment. As a result, a shaft is driven, which in turn adjusts the seat structure of the vehicle seat by means of a gearing. During the pumping motion of a lever, a force is transmitted by means of an entraining element, which engages a gear. At the same time, a freewheel is released, which prevents the shaft from rotating back in the blocked direction. Since the lever is manually actuated, the possible swing range of the lever in each direction is limited to about 20xc2x0 to 25xc2x0.
In accordance with one aspect of the present invention, an improved seat height adjuster drive is provided. In accordance with this aspect, the seat height adjuster drive includes a drive with a manually actuatable lever mounted for movement from an idle position within two sector ranges that are different from one another. The drive is responsive to movement of the lever within a first of the sector ranges to rotate a rotatable component of the drive and thereby cause movement of the drive in a first adjustment direction. The seat height adjuster drive also includes a releasable freewheel for releasably blocking rotation of the rotatable component. The releasable freewheel is responsive to movement of the lever through a second of the sector ranges to allow movement of the drive in a second adjustment direction.
As a result of having different sector ranges for both directions of adjustment (namely asymmetric with respect to the idle position), a larger swing range of the lever is available for one adjustment direction (preferably the upward movement). In comparison with the state of the art, it is therefore possible to reduce, with the same sum of the sector ranges, selectively the number of necessary lever strokes, or to increase the transmission. In the latter case, a smaller leverage needs to be applied, and the capacity of absorbing crash forces is increased. Preferably, the upward directed adjustment of the vehicle seat occurs upward in a pumping motion by means of the lever, whereas the downward directed adjustment of the vehicle seat occurs downward by a downward movement, which is released, for example, by the lever. The downward movement may then occur alone with the aid of the force of weight.
It will be of advantage, when the freewheel can be released in two directions independently of the drive. As a block, the freewheel prevents an unwanted rotation of a shaft. In the case of the adjustment direction with the smaller swing range (normally the downward direction), it is possible to release the freewheel such that the component of the seat height adjuster drive that is to be moved, for example, a shaft, is capable of performing a plurality of rotations. This permits the downward movement in one step assisted by the force of weight. To be able to use components that are easy to make, the freewheel preferably comprises operative surfaces arranged on the outside, preferably integral with the seat structure. The freewheel is designed and constructed preferably symmetrical in both directions of rotation. To be able to release the freewheel in both directions of rotation as desired, it is preferred to provide a switch that is actuated by the lever. To be able to release the freewheel independently of the drive, the freewheel comprises a plate cam for its release. To this end, the plate cam is to be moved opposite to the direction of movement of the lever. Preferably, the switch cooperates with a guide track arranged on the lever. The guide track is used to predetermine the possible sector ranges for the movement of the lever, which are defined by stops.
Preferably, a pawl is provided for a positive drive of a gear. The drive may also be nonpositive, for example by a further freewheel. In a preferred embodiment, springs that engage the pawl may be used both to keep the lever in its idle position or return it to same, and to engage and hold the pawl against the gear. In comparison with the known seat height adjuster drive, the drive of the present invention can do with a lesser number of components for securing the idle position of the lever, for example with two simple tension springs without additional components. The pawl is movable at least in part independently of the lever, preferably by being pivotably mounted to a guide bar. This enables an advance movement of the lever, for example, for releasing the freewheel. At the same time, the pawl may serve as an antirotation device, i.e., prevent unwanted rotations of the gear caused by vibratory loads. In the idle position, a connecting pin may lie between the pawl and guide bar against the housing of the seat height adjuster drive, and the pawl may be supported on the lever.
In a preferred embodiment, a loop or friction spring is provided, which is used to disengage the pawl from the gear. As a result, the lever is able to return quietly, i.e. without a so-called xe2x80x9crattle.xe2x80x9d The use of the friction spring is not limited to the seat height adjuster drive of the present invention. Rather, it may be used in any stepping mechanism or the like, wherein toothed surfaces must be guided past one another, which should occur quietly. For example, the friction spring opens when being entrained by the guide bar. It closes upon contact with the pawl, and otherwise it tightens to a certain extent, i.e., it moves relative to the body, about which it loops, not because of friction. Depending on the geometric design of the ends of the friction spring, entrainment by the guide bar may occur always at the same end or at the end leading in the direction of rotation.
In a preferred embodiment, the control elements for switching the freewheel are adapted for moving at least in part axially with respect to the freewheel. It is thus possible to release the freewheel in different directions. As a result, the drive for the freewheel is simplified, which makes manufacture more cost-favorable. In addition, it is possible to reduce the necessary installation space. Preferably, in one of the two directions of rotation the freewheel is releasable merely in the circumferential direction (azimuthally) by moving the control elements, whereas it is released in the other direction of rotation by turning the axial movement of the control elements into a movement in the opposite circumferential direction. The change occurs preferably by oblique surfaces. For the first-mentioned direction of rotation, the releasing movement of the freewheel is separated from the axial movement of the control elements.
To trigger the axial movement of the control elements, it is preferred to provide balls, which extend in the radial direction, and which are arranged in the circumferential direction evenly about the axis of rotation of the freewheel. Preferably, the balls are guided in guide tracks, which have a nonconstant cross section in the axial direction. A movement of the balls in the circumferential direction will then be able to cause the desired axial movement. For reasons of wear and tear, the balls preferably do not act directly upon the component with the control elements. Instead, a flat thrust washer is arranged between the balls and the control elements.
The term xe2x80x9cseat height adjusterxe2x80x9d is to be understood to include likewise mixed seat height and inclination adjusters, as well as mere seat inclination adjusters, wherein, for example, only certain areas of the seat change their height relative to other areas of the seat. The drive of the present invention may accordingly be used in many ways in different vehicle seats.